Automatic seat latch unlocking apparatus and circuit therefor

ABSTRACT

A solenoid having a pull-in coil and a hold-in coil is adapted to be mounted within the seat back of the front seat of a vehicle such that the plunger associated with the solenoid can be actuated to release the seat locking mechanism. As one of the doors of the vehicle is opened, the solenoid is actuated to unlock the seat-locking mechanism and maintain the mechanism unlocked to allow the seat backs to be moved forward. The pull-in coil is automatically actuated for a predetermined time sufficient to ensure the plunger has been moved to unlatch the locking mechanism after which the pull-in coil is deactuated. The hold-in coil is continuously actuated while the vehicle door is open.

1451 Sept. 25, 1973 AUTOMATIC SEAT LATCH UNLOCKING APPARATUS AND CIRCUITTHEREFOR Primary Examiner-Herman J. Hohauser [75] Inventor: Thomas A.Wright, Grand Rapids Attorney price Hencveld Huizenga & Cooper Mich.[57] ABSTRACT [73] Asslgnee: HI'Ram Grandvlue Mlch A solenoid having apull-in coil and a hold-in coil is [22] Filed: July 10, 1972 adapted tobe mounted within the seat back of the front I seat of a vehicle suchthat the plunger associated with [21 1 App, 270452 the solenoid can beactuated to release the seat locking mechanism. As one of the doors ofthe vehicle is [52] US. Cl. 307/10 R, 317/155, 180/112 p the solenoid iactuated t nlock he seat- [51] Int. Cl. 862d 45/00 locking mechanism andmaintain the mechanism n- [58] Field of Search 317/155, D161 7; lockedto allow he ea backs to be moved forward.

307/9, 10 R, 141, 141.4, 141.8; 180/82, 103, The pull-in coil isautomatically actuated for a prede- 1 12 termined time sufficient toensure the plunger has been moved to unlatch the locking mechanism afterwhich [56] R f n Cit d the pull-in coil is deactuated. The hold-in coilis contin- UNITED STATES PATENTS uously actuated while the vehicle dooris open.

3.456.164 7/1969 Sternberg 317/155 x 9 Claims, 6 Drawing Figures DRIVER\PASSENGER 1 F SEAT v SEAT ACTU. ACT U.

SOL. SOL.

CONTROL RELAY CKT.

PATfiNTfiusl-irzslm 3.781.730

I SHEET 1 or:

FIG. I

TO COURTESY 1 LIGHT SWITCH PRIOR ART T F IG. 2

DRIVER 50 60\PASSENGER SEAT 70 f SEAT ACTU' ACTU. SOL. SOL

I I sz/M C r D 62 HL J 40 B CONTROL T RELAY CKT.

y FIG. 3

PAn-jmmscrzsms SHEET 2 BF 2 I DRIVER PASSENGER 54 3 56' SEAT SEAT ACTU.64 SOL.

l I 52% B 3 I. 55 M C l CONTR AUTOMATIC SEAT LATCH UNLOCKING APPARATUSAND CIRCUIT THEREFOR BACKGROUND OF THE INVENTION The present inventionrelates to an apparatus for automatically unlatching the locked seatback of a vehicle, and particularly to a novel electrical circuit andsolenoid for use therewith.

With the advent of federal safety regulations requiring that the movablefront seat backs of vehicles be locked in the upright position, automanufacturers have installed latches in their two-door automobiles tosatisfy the requirements. The latcheshave levers which can be manuallytripped to release the locking or latching mechanism such that apassenger can move the seat back forward to enter the rear seat area ofthe automobile. When the seat back is returned to the upright position,it is again securely locked in place.

Recently, some top-of-the-Iine automobiles have employed an electricallyoperated solenoid which is actuated by the courtesy light switch in theautos to automatically release the locking mechanism for the seat backwhen one of the doors have been opened. Thus, it is no longer necessarywith this type of arrangement to manually trip a lever to gain entranceto the rear seat. Although greatly adding to the convenience forpassengers, such apparatus is a relatively expensive feature andsometimes is troublesome and erratic in operation. Existing automaticsolenoid apparatus employ a two-coil solenoid, one coil being employedto initially provide a relatively high pull-in force for the plunger ofthe solenoid, while the second coil being employed to provide a lowerholding force to maintain the seat in the unlockedposition while thepassengers are entering the vehicle. The coils are coupled to theelectrical system of the automobile by means of a mechanically peratedelectrical switch mounted within the solenoid and which is tripped bythe movement of the solenoid plunger to convert the system from thepull-in mode of operation to the hold-in mode of operation byalternately switching the pull-in and hold-in coils into operation.

Such an arrangement has provided unsatisfactory performance .andrelatively high cost since the solenoid must be mounted in the seat backin relatively critical alignment to ensure that the plunger properlyactuates the mechanical switch within the solenoid as the plunger isactuated. Frequently, misalignment during the installation of thesolenoid in the seat back during the manufacture of the automobile,causes the plunger to bind thereby not fully contacting the mechanicalswitch at the end of the plunger travel. The result is that frequentlythe pull-in coil will pulse in and out causing an audible noise commonlyreferred to as machine gunning" which is rather offensive and tends toburn out the solenoid.

In some instances, the pull-in coil can be continuously actuated andwill overheat or cause a circuit breaker in the electrical circuit toinactivate the device, making it impossible for the seat back to bemoved forward. Thus, the automatically operating solenoids of the priorart have proven unsatisfactory as to their operational characteristicsand are relatively costly since they require critical alignment and aspecial internally mounted switch.

SUMMARY OF THE INVENTION The solenoid and control circuit of the presentinvention, however, does not employ a switching arrangement built withinthe solenoid and which relies on the solenoid plunger travel. Instead,the system of the present invention uses a solenoid having two coils,one for pulling in the solenoid plunger and a second coil for holdingthe solenoid plunger in. The coils are automatically operated by anelectrical circuit which can be remotely positioned and which suppliesthe pull-in coil with a pulse of predetermined duration sufficientlylong to ensure that the solenoid plunger is pulled in. The circuit thenautomatically removes the power to the pullin coil while continuouslyapplying power to the hold-in coil. The solenoid does not, therefore,rely on the plunger movement in switching from the pull-in to thehold-in mode of operation. Additionally, the solenoid is simpler inconstruction since it requires no internally mounted switch. Finally,since the plunger travel is less critical, installationis considerablyeasier thereby further reducing the cost of such a feature to the autobuyer.

Apparatus embodying the present invention comprises an electricallyoperated solenoid having a plunger adapted to unlatch the lockingmechanism of a vehicle seat back and an electrical control circuittherefor. The solenoid includes a pull-in coil and a hold-in coil, thepull-in coil being actuated by the electrical circuit for apredetermined period of time when the vehicle door is opened and thendeactivated while the hold-in coil has continuous power applied to it tohold the solenoid plunger in the unlatched position when the vehicledoor is opened.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial side elevationalview of a vehicle seat showing the position of a solenoid forautomatically releasing the seat back locking mechanism;

FIG. 2 is a schematic diagram showing the automatic unlatching mechanismof the prior art and the electrical control therefor;

\ FIG. 3 is an electrical circuit diagram partially in schematic andblock form showing one embodiment of the present invention;

FIG. 4 is an electrical circuit diagram in schematic form showing oneportion of the circuitry shown in block form in FIG. 3;

FIG. 5 is an electrical circuit diagram partially in schematic and blockform showing an alternative embodiment of the present invention; and

FIG. 6 is an electrical circuit diagram in schematic form showing thedetails of one portion of the circuitry 'shown in block form in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a vehicleseat 10 which is a front bucket-type seat employed in automobiles of atwo-door design. The seat comprises a seat portion 12 and a hinged backportion 14 which can be moved forwardly to permit access to the rearseat of the automobile (not shown). The seat further includes a latchingmechanism 15 (shown in block form) for locking the seat back 14 in anupright position. The latching mechanism includes a release pin 16 and asolenoid 20 having a casing 27 and a plunger 22 with a hooked end 24which engages the release pin 16. When solenoid is actuated, the releasepin 16 will be pulled by the end 24 of the moving plunger 22 therebyunlatching the seat back such that it can be moved forwardly. If isnoted that the release pin is spring loaded and holds the plunger 22 inits extended position when the seat back is locked in the uprightposition.

FIG. 2 shows the prior art apparatus for controlling a solenoid 20 suchthat it will provide a relatively high pull-in force necessary toinitially release the locking mechanism by overcoming the resistiveforce of the release pin 16. Once the plunger 22 of the solenoid 20 hasbeen retracted, however, it is unnecessary to apply as large a pullingforce, a lesser force being adequate to hold the plunger in itsretracted position whereby the seat latch is' in the unlocked position.This dual force arrangement is accomplished by the circuitry of FIG. 2in which the plunger 22 is illustrated in pictorial form and themechanical equivalent of the release pin 16 is shown as a spring 24anchored to a fixed member 26. When the seat back is in its lockedupright position, the solenoid plunger 22 will be moved towards theright side as indicated by the arrow labeled latched.

It is convenient to employ the courtesy light switch as a control meansfor unlatching the seat back since the seat back 14 (FIG. 1) normally ismoved forward when one of the doors is opened. This is accomplished bymeans ofa relay 30 (FIG. 2) which is coupled to the courtesy lightswitch such that when the courtesy lights are actuated by opening adoor, the relay 30 having contacts 32 associated therewith issimultaneously actuated. Relay 30 is of the normally open type and theswitch contacts 32 are coupled between the positive supply bus coupledto the automobile battery (in a negative ground system) and two coils 21and 23 associated with the solenoid 20. The coil 21 is the pull-in coiland the coil 23 is the hold-in coil.

As seen in FIG. 2, a switch 35 has one set of contacts 36 in series withthe pull-in coil 21 and another set of contacts 37 in series with thehold-in coil 23. The

switch 35 is physically mounted within the solenoid 20 such thatcontacts 36 will be closed when the plunger is in its extended orlatched position to the right, and will be opened when the plunger ismoved to its retracted positions within the solenoid housing, asillustrated in FIG. 2. The mechanical coupling of the switch contacts 36and 37 of switch 35 to the plunger 22 of the solenoid 20 is representedby the dotted lines in the figure. Switch 37 will normally be open whenplunger 22 is in its extended (latched) position and will close when theplunger has been pulled into its retracted position. In'someapplications, the switch 37 can be omitted and coil 23 directly coupledto ground.

The circuit of FIG. 2 is shown with the relay in the unlatched position.The holding coil 23 is actuated by means of power applied through theclosed contacts 32 of the relay 30, through a current-limiting resistorin series with the holding coil 23, and the closed contact 37 whichcompletes the circuit path between the positive supply bus and ground.

Once the door of the vehicle has been closed, contacts 32 will openthereby disconnecting the voltage source from the relay coils 21 and 23and the plunger 22 will be returned to its locked position by the springbias 23 of the release pin 16 (FIG. 1). In this position, the contacts36 of the mechanical switch 35 will be closed and the contacts 37 willbe opened. Once the vehicle door is reopened the contacts 32 are againclosed and switch 36 will initially actuate the pull-in coil 21 to causethe plunger to move and actuate switch 35 such that contacts 36 open andcontacts 37 close. The making and breaking of the contacts 36 iscritical since the pull-in coil 21 draws a considerable amount ofcurrent necessary to initially overcome the resistive force of therelease pin 16.

If the housing 27 of the solenoid 20 is misaligned in the seat back 14during installation and the plunger 22 binds against surrounding partsof the seat back 14 or the locking mechanism, the plunger 22 may notretract fully enough to open switch contacts 36 and the excessivecurrent drawn through the pull-in coil 21 will, within a short period oftime, cause the circuit breaker or fuse of the electrical system tobecome actuated. Altemately, if the plunger 22 moves sufficiently toinitially open the switch 36 but not close the switch 37, the plungerwill again return to its latched position thereby causing the switch 36to close causing the plunger 22 to again move toward the unlatchedposition. This cycle may repeat at a relatively high frequency toproduce the objectionable machine gunning noise. Thus, the switchingarrangement incorporated in the solenoid 20 of the prior art shown inFIG. 2 has proven unsatisfactory.

Referring now to FIG. 3, there is shown a solenoid and circuitarrangement which overcomes the deficiency of the prior art as notedabove and which employs a time-delayed control relay circuit 40 toprovide the desired control. There is shown in FIG. 3 a solenoid 50which is on the driver's side and a solenoid 60 on the pasengers side.Each solenoid has a plunger 52 and 62 which corresponds to the plunger22 of the solenoid shown in FIG. 1. The solenoids 50 and 60 can beidentical and include pull-in coils 54 and 64 and hold-in coils 56 and66. In some applications the solenoid plungers 52 and 62 may actually bepushed instead of pulled by the coils 54 and 64 respectively; thecontrol circuit, however, remains the same.

A door jam or courtesy light switch is coupled in series between apositive terminal of the automobile supply voltage and a terminal C ofthe control relay circuit 40. Terminal C is also directly coupled to theholdin coils 56 and 66 of the solenoids 50 and 60 respectively. It isseen, therefore, that when the switch 70 is actuated by opening one ofthe doors, the hold-in coils 56 and 66 are actuated. A terminal B of thecircuit 40 is coupled to the negative or ground supply of the vehicleand a terminal D is coupled to the pullin coils 54 and 64 of thesolenoids 50 and 60 respectively. The control relay circuit serves toprovide a voltage pulse of a predetermined duration at terminal D whichis sufficient to cause the solenoid plungers 52 and 62 to initiallyovercome the holding tension of the locking mechanism 15 (FIG. 1) suchthat they will unlatch the seat back. The control circuit 40accomplishes this function by momentarily closing the contacts 42 shownin phantom form in FIG. 3 by means of the circuitry of circuit 40 whichis shown in detail in FIG. 4.

Referring now to FIGS. 3 and 4, it is seen that the terminal B isgrounded and that terminal C is coupled to the positive voltage supplywhen the courtesy light switch is closed. The control circuit 40 of FIG.4 includes a control relay coil 41 having a pair of normally opencontacts 42 which are coupled between terminal A and D as shown. Therelay coil 41 has one terminal coupled to terminal C and the otherterminal coupled to a collector terminal 440 of a first transistor 44.An emitter terminal 44c of transistor 44 is coupled directly to terminalB. A base terminal 44b of transistor 44 is coupled to terminal C bymeans of a first resistor 45 and a second resistor 46 coupled in seriesfrom terminal 44b to terminal C. The junction of resistors 45 and 46 iscoupled to a second transistor 48 at a collector terminal 480 thereof.An emitter terminal 48a of transistor 48 is coupled directly to terminalB. A base terminal 48b of transistor 48 is coupled to terminal C bymeans of a third resistor 49 and to terminal B by means of a fourthresistor 51. A capacitor 52 is coupled in parallel with resistor 51.

In operation, as the vehicle door is opened, switch 70 will closethereby applying the positive voltage from the battery of the vehicle tothe hold-in coils 56 and 66 of the solenoids'50 and 60 respectively aswell as to terminal C of the control circuit of FIG. 4. At this time, itis also desired to actuate the pull-in coils 54 and 64. This isaccomplished by applying power coupled from terminal A of the circuit toterminal D of the circuit through the closed contacts 42 of the relay4]. Relay coil 41 is actuated as the voltage is applied to terminal C bymeans of transistor 44 which conducts as-voltage is initially applied toterminal C. The collector current of transistor 44 is sufficient tocause the relay coil 41 to pull the contacts 42 to the closed positionthereby applying the positive voltage from the battery through contacts42 to the pull-in coils 54 and 64 of solenoids 50 and 60 respectively.

It is noted that at this time (i.e., when the voltage at terminal C isinitially applied) capacitor 52 will be uncharged and transistor 48 willbe nonconductive. As the switch 70 remains closed and applies power toterminal C, however, capacitor 52 will charge through the resistor 49until the transistor 48 is forward biased and conducts. Collectorcurrent for transistor 48 is supplied through the collector resistor 46coupled to terminal C. As transistor 48 is rendered conductive, thecollector voltage at terminal 480 will decrease markedly. Since thecollector terminal 48c is coupled by means of resistor 45 to the baseterminal 44b of transistor44, as the collector voltage of transistor 48decreases, it will pull down the base voltage of transistor 44 until thelatter transistor becomes nonconductive. As this occurs, the currentthrough relay coil 41 is cut off and contacts 42 will open therebyremoving the power from the pull-in coils 54 and 64 of solenoid 50 and60 respectively.

The time that transistor 44 is conductive to allow the contacts 42 toremain closed is dependent upon the charging time constant of thecapacitive-resistive network 52 and 49 together with the biasing of thetransistors 44 and 48. The value of resistors 49 and capacitor 52 ischosen such that transistor 44 is conductive for a period long enough toensure that the solenoid plungers 52 and 62 have been pulled in to theirunlatched position. In one embodiment, 100 milliseconds was a sufficientperiod of time to ensure this operation. Resistor 51 serves as a bleederresistor once the circuit has been inactivated to discharge capacitor52. The solenoid shown in FIG. 3 can be incorporated into the seat backin a manner similar to that shown in FIG. I to provide the desiredunlatching of the locking mechanism.

An alternative embodiment for use with a groundingtype of courtesy lightswitch and which employs a single winding within the solenoid and a tapterminal to form the pull-in and hold-in coils is shown in FIGS. 5 and6. The control relay circuit 55 is modified to provide the desired dualcontrol through the solenoids by first applying power to terminal E fromthe positive supply bus of the vehicle through closed contacts 64 (FIG.5) and simultaneously grounding terminal D through closed contacts 62.Thus, during the pull-in mode of operation, coils 54, 56', 64', and 66are all actuated to provide a maximum pull-in force for the associatedplungers 52' and 62' of solenoids 50 and 60' respectively.

After a predetermined time delay, contacts 62' open and pull-in coils54' and 64' are thereby electrically disconnected from the power supply.This terminates the pull-in mode of operation since the plungers 52' and62 have had sufficient time to retract and unlatch the seat-lockingmechanism. Hold-in windings 56' and 66 remain activated to hold the seatlocking mechanism in the unlatched position. This dual control effect isachieved by means of the circuitry shown in detail in FIG. 6 whichoperates the relay contacts 62 and 64 (FIGS. 5 and 6) to actuate thepull-in and hold-in coils 54', 56', 64', and 66' respectively.

Control circuit 55 includes a first relay coil 63 having one terminalcoupled to terminal B and another terminal coupled to terminal A. Relaycontacts 64 are coupled between terminals B and E and are associatedwith coil 63. These contacts close when the coil 63 is activated. Thecontrol circuit 55 includes a second relay coil 61 which, when actuated,closes the associated contacts 62 to ground terminal D during the pullin mode of operation. One terminal of the relay coil 61 is coupled tothe positive supply bus by means of terminal B while the other terminalof relay coil 61 is coupled to a collector terminal 650 of a firsttransistor 65. An emitter terminal 65a of transistor 65 is directlycoupled to terminal A. A base terminal 65b of transistor 65 is coupledto terminal B by serially coupled resistors 66 and 67. The junction ofresistors 66 and 67 is coupled to a collector terminal 680 of secondtransistor 68. The emitter terminal 68c of transistor 68 is coupleddirectly to terminal A. A base terminal 68b of transistor 68 is coupledto terminal B by means of a resistor 71, and to terminal A by means of aresistor 69. Capacitor 72 is coupled in parallel with resistor 69.

In operation, the circuitry shown in FIGS. 5 and 6 operates to actuatethe pullin coils 54' and 64' momentarily as the courtesy light switch70' (FIG. 5) is actuated by initially closing both relay contactswitches 62 and 64. Transistor 65 conducts momentarily and the collectorcurrent therethrough actuates relay coil 611 to close contact 62 therebygrounding the terminal D and coupling the pull-in coils 54' and 64' inthe circuit. Once capacitor 72 has charged sufficiently to rendertransistor 68 conductive, transistor 65 will be rendered nonconductiveand the relay contact switch 62 will open and disconnect the pull-incoils 54' and 64'. it is noted that the hold-in coils 56' and 66' whichare directly actuated by the relay coil 63 and continuously operate whenthe switch 70 is closed, will remain in the circuit to hold the plungers52 and 62' in the retracted position.

In this manner, therefore, the desired dual control of the solenoids isachieved with the grounding-type of courtesy light switch and with asingle winding for each solenoid, the single winding having a tapterminal to define the pull-in and hold-in coils. It will becomeapparent to those skilled in the art that various modifications to thecontrol circuit and the solenoid construction can be made withoutdeparting from the spirit and scope of the present invention as definedin the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows.

1. An apparatus for automatically unlatching a seat back of a vehiclecomprising:

a locking mechanism adapted to be mounted within the seat back of avehicle and which includes a release mechanism;

a solenoid having a movable plunger adapted to be fitted within saidseat back of said vehicle such that said movable plunger engages saidrelease mechanism therein, said solenoid further comprising a pull-incoil and a hold-in coil; and

control means for activating said pull-in coil by supplying current tosaid pull-in coil for a predetermined time to provide a pulling force onsaid plunger sufficient to unlatch said locking mechanism and thendeactivating said pull-in coil while supplying current to said hold-incoil to provide a holding force on said movable plunger sufficient tohold said movable plunger in position to maintain said locking mechanismin its unlatched position.

2. The apparatus of claim 1 wherein said pull-in coil and said hold-incoil are formed from a single winding having terminals at either endthereof and having a tap terminal at a point between said end terminals,said pull-in coil being between one end terminal and said tap terminal,and said hold-in coil being between the other end terminal and said tapterminal.

3. The apparatus of claim 1 wherein said control means comprises asource of operating potential and a time-delay relay coupled in seriesbetween said pull-in coil and said source of operating potential foractuating said coil for a predetermined period of time.

4. The apparatus of claim 1 and further comprising means for actuatingsaid control means when a door of said vehicle is opened.

' 5. The apparatus of claim 4 wherein said actuating means comprises acourtesy light switch mounted on said vehicle such that said switch isactuated when said vehicle door is opened.

6. A seat back release mechanism comprising:

a vehicle having a releasable locking mechanism for locking a vehicleseat back in a predetermined position;

a solenoid having a pull-in coil, a hold-in coil and a plunger, saidplunger mechanically coupled to said locking mechanism such that whensaid plunger is moved by actuating said solenoid, said locking mechanismis unlocked thereby allowing said seat back to be moved; and

a control circuit for applying current of a sufficient magnitude to saidpull-in coil for a predetermined time, to apply a pulling force on saidsolenoid plunger sufficient to unlatch the releasable locking mechanism,said circuit additionally applying current to said hold-in coilsufficient to provide a lesser holding force to said plunger to maintainthe locking mechanism in an unlocked position.

7. The apparatus of claim 6 in which said vehicle includes an electricalswitch operated by the opening of a door of said vehicle and saidcontrol circuit is coupled to said switch to be activated when saidvehicle door is opened.

8. The apparatus of claim 7 wherein said control circuit comprises arelay having a pair of contacts coupled in series between a source ofoperating potential and said pull-in coils, and a relay coil; atransistor having base, collector, and emitter terminals, said collectorand emitter terminals coupled between said relay coil and said source ofoperating potential such that collector current in said transistorcontrols the closure state of said relay contacts; and time-delay meanscoupled to the base terminal of said transistor for controlling theconduction of said transistor such that said pull-in coil is activatedfor said predetermined time.

9. The apparatus of claim 8 wherein said time-delay means comprises aresistor serially coupled to a capacitor, the combination coupled tosaid source of operating potential; and a second transistor having base,collector and emitter terminals, said collector terminal of said secondtransistor coupled to said base terminal of said transistor, said baseterminal of said second transistor coupled to one terminal of saidcapacitor, and said emitter terminal of said second transistor coupledto the other terminal of said capacitor such that as said capacitorbecomes charged, said second transistor conducts thereby causing saidtransistor to become nonconductive and said relay contacts to openthereby inactivating said pull-in coil after said predetermined time.

* i i i i

1. An apparatus for automatically unlatching a seat back of a vehiclecomprising: a locking mechanism adapted to be mounted within the seatback of a vehicle and which includes a release mechanism; a solenoidhaving a movable plunger adapted to be fitted within said seat back ofsaid vehicle such that said movable plunger engages said releasemechanism therein, said solenoid further comprising a pull-in coil and ahold-in coil; and control means for activating said pull-in coil bysupplying current to said pull-in coil for a predetermined time toprovide a pulling force on said plunger sufficient to unlatch saidlocking mechanism and then deactivating said pull-in coil whilesupplying current to said hold-in coil to provide a holding force onsaid movable plunger sufficient to hold said movable plunger in positionto maintain said locking mechanism in its unlatched position.
 2. Theapparatus of claim 1 wherein said pull-in coil and said hold-in coil areformed from a single winding having terminals at either end thereof andhaving a tap terminal at a point between said end terminals, saidpull-in coil being between one end terminal and said tap terminal, andsaid hold-in coil being between the other end terminal and said tapterminal.
 3. The apparatus of claim 1 wherein said control meanscomprises a source of operating potential and a time-delay relay coupledin series between Said pull-in coil and said source of operatingpotential for actuating said coil for a predetermined period of time. 4.The apparatus of claim 1 and further comprising means for actuating saidcontrol means when a door of said vehicle is opened.
 5. The apparatus ofclaim 4 wherein said actuating means comprises a courtesy light switchmounted on said vehicle such that said switch is actuated when saidvehicle door is opened.
 6. A seat back release mechanism comprising: avehicle having a releasable locking mechanism for locking a vehicle seatback in a predetermined position; a solenoid having a pull-in coil, ahold-in coil and a plunger, said plunger mechanically coupled to saidlocking mechanism such that when said plunger is moved by actuating saidsolenoid, said locking mechanism is unlocked thereby allowing said seatback to be moved; and a control circuit for applying current of asufficient magnitude to said pull-in coil for a predetermined time, toapply a pulling force on said solenoid plunger sufficient to unlatch thereleasable locking mechanism, said circuit additionally applying currentto said hold-in coil sufficient to provide a lesser holding force tosaid plunger to maintain the locking mechanism in an unlocked position.7. The apparatus of claim 6 in which said vehicle includes an electricalswitch operated by the opening of a door of said vehicle and saidcontrol circuit is coupled to said switch to be activated when saidvehicle door is opened.
 8. The apparatus of claim 7 wherein said controlcircuit comprises a relay having a pair of contacts coupled in seriesbetween a source of operating potential and said pull-in coils, and arelay coil; a transistor having base, collector, and emitter terminals,said collector and emitter terminals coupled between said relay coil andsaid source of operating potential such that collector current in saidtransistor controls the closure state of said relay contacts; andtime-delay means coupled to the base terminal of said transistor forcontrolling the conduction of said transistor such that said pull-incoil is activated for said predetermined time.
 9. The apparatus of claim8 wherein said time-delay means comprises a resistor serially coupled toa capacitor, the combination coupled to said source of operatingpotential; and a second transistor having base, collector and emitterterminals, said collector terminal of said second transistor coupled tosaid base terminal of said transistor, said base terminal of said secondtransistor coupled to one terminal of said capacitor, and said emitterterminal of said second transistor coupled to the other terminal of saidcapacitor such that as said capacitor becomes charged, said secondtransistor conducts thereby causing said transistor to becomenonconductive and said relay contacts to open thereby inactivating saidpull-in coil after said predetermined time.